This invention relates to an automotive vehicle framing system, and particularly to a vehicle framing system that includes a hollow sill having enhanced resistance against bending or torsional load forces while providing optimal vibration characteristics, also considering impact concerns.
A typical automotive or light truck body would include underbody frame rails and body side apertures/sides sills that form the door surround structure. These are major structural components that determine overall body stiffness and the location of the first torsion and bending nodes. The present invention is concerned with the strengthening of these structures, in this case with a variable cross section structural foam. The varied cross section would be used to position the node for optimal vibration characteristics for the vehicle occupants and improved impact response, without unduly increasing the weight of the vehicle.
One preferred embodiment of the invention includes a tubular side structure that has an elongated hollow sill with a rigid lightweight insert extending within the hollow sill to surrounded by structural polymer foam give the sill an enhanced resistance against bending or torsional load forces.
In order to minimize the overall weight of the side frame, a relatively lightweight elongated three dimensional core is located within the sill; the rigid polymer foam has an inner surface bonded to the elongated core, and an outer surface bonded to the interior surface of the hollow sill. The core is preferably formed as a hollow tubular element to reduce the core weight. The light weight core occupies a significant portion of the sill interior space, thereby reducing the amount (mass) of rigid polymer foam required to stiffen the hollow sill against bending or torsional load forces.
Specific features of the invention will be apparent from the attached drawings and description of a preferred embodiment of the invention.